scalaz’Functor如何被赋予具有上下文绑定的更高级别的类型？

class RequiresManifest[A: Manifest] {
  def value: A
}

class RequiresAnyRef[A <: AnyRef] {
  def value: A
}

class RequiresBothManifestAndAnyRef[A <: AnyRef: Manifest] {
  def value: A
}

这可能吗 ？或者可以定义’BoundedFunctor特征？这样的事情：

trait BoundedFunctor[F[_],Bound[_]] {
  def fmap[A: Bound,B: Bound](r: F[A],f: A => B): F[B]
}

这是我的激励示例：如何为TypedConverter类定义Functor.

import com.thoughtworks.xstream.converters.Converter

abstract class TypedConverter[A <: AnyRef: Manifest] extends Converter { 
  final def canConvert(klass: Class[_]) = 
    manifest[A].erasure.isAssignableFrom(klass)

  final def marshal(value: AnyRef,writer: HierarchicalStreamWriter,context: MarshallingContext) =
    typedMarshal(value.asInstanceOf[A],writer,context)

  final def unmarshal(reader: HierarchicalStreamReader,context: UnmarshallingContext) = 
    typedUnmarshal(reader,context)

  def typedMarshal(value: A,context: MarshallingContext): Unit

  def typedUnmarshal(reader: HierarchicalStreamReader,context: UnmarshallingContext): A
}

这种更高级的类型对其类型参数有两个约束,第一个是Manifest,因为它用于’canConvert’的实现,第二个是AnyRef,因为unmarshal需要一个Object.

实际上我正在尝试创建一个InvariantFunctor,但Functor将会开始.